The present invention relates to ductwork and particularly to joint construction therefor.
Ductwork for heating and cooling systems are typically fabricated on-site particularly in commerical installations which require frequent joining of duct sections each of which are several feet long. The joint construction can and has usually been accomplished by overlapping the ends of sections of cylindrical pipes and welding or riveting the ends together. With smaller ducts, the joints particularly for elbows can be prefabricated by spin forming overlapping U-shaped mating ends. Such construction, however, is not normally employed in commercial duct construction since the ductwork typically is significantly larger and of heavier gage and does not lend itself to prefabricated and assembled sections.
Although the practice of riveting or welding duct sections together has been commercially feasible, the time involved in assembling such ductwork employing such techniques at a job site is considerable and once sections of ducts are joined, the connection is essentially permanent and not easily changed. Thus, there exists a need for a duct joint construction which permits on-site fabrication and ease of assembly particularly for relatively heavy gage and large diameter ducts used in commercial installations.